Varietal Preferences of Erythroneura Leafhoppers (Homoptera: Cicadellidae) Feeding on Grapes in New York

Species composition of Erythroneura leafhoppers infesting the 3 major classes of grapes grown in New York was investigated. Eastern grape leafhopper, E. comes (Say), comprised 74-100% of populations collected on the native American (Vitis labrusca Bailey) cultivars ‘Concord', ‘Niagara', ‘Catawba' and ‘Delaware'. On interspecific hybrid (Vitis sp.) and Vitis vinifera L. cultivars, E. comes was largely absent, and 97-100% of leafhoppers collected were 2 cryptic species, E. bistrata McAtee and E. vitifex Fitch. On the native American variety ‘Elvira', a V. labrusca X V riparia Michaux hybrid, field populations were 24% E. comes and 74% the E. bistrata/vitifex complex. E. vitis (Harris), E. tricinta Fitch, and E. vulnerata Fitch were also present in commercial grapes, but never exceeded 20% of the populations sampled. Populations on wild V. riparia adjacent to vineyards were comprised of 24% E. comes, 47% E. histrata/vitifex, 19% E. vitis, and 10% E. tricinta. Dissection revealed that proportions of E. bistrata and E. vitifex in field collections, varied from 97% E. bistrata to 61% E. vitifex. Oviposition of E. comes and E. bistrata on V. vinifera, interspecific hybrid, and native American cultivars was compared in greenhouse choice tests and field no-choice tests. In choice tests, E. comes laid more eggs on Concord and Elvira than on the interspecific hybrid ‘Seyval blanc', or the V. vinifera cultivar ‘White Riesling'. E. bistrata did not oviposit on Concord when paired with either Elvira, Seyval blanc or White Riesling. When caged to grape leaves in no-choice tests, E. comes laid the most eggs on native American cultivars and the fewest on V. vinifera and interspecific hybrids; E. bistrata laid the most eggs on hybrid and V. vinifera cultivars, and very few eggs on three native American cultivars. These results show that E. bistrata and E. vitifex are the principal pest species on V. vinifera and many interspecific hybrid cultivars in New York, and that E. comes is the principal leafhopper pest on native American V. labrusca cultivar

Influence of Temperature-Driven Phenology and Photoperiodic Induction of Reproductive Diapause on Population Dynamics of Erythroneura comes (Homoptera: Cicadellidae)

The influence of degree-day accumulations and photoperiodic induction of diapause on the phenology of Erythroneura Comes (Say) was investigated. In growth chamber experiments, nymphs reared at photoperiods of 710 degree days (DD) before 1 August are required to produce a 2nd generation of E. comes under climatic conditions in New York.Variationsin temperature-driven development are hypothesized to strongly influence year-to-year variability in leafhopper abundance. Degree-day accumulations by 30 June correlated well with degree-days by 1 August and may provide a useful early-warningsystem for predicting years in which leafhopper population densities are above averag

Phenology, Within-Vineyard Distribution, and Seasonal Movement of Eastern Grape Leafhopper (Homoptera: Cicadellidae) in New York Vineyards

Seasonal changes in within-vineyard distribution and abundance of Erythroneura comes (Say) adults and nymphs were investigated from 1989 to 1992. Trap catches of adults were highest in May and were concentrated in wooded areas next to vineyards. In 1989 and 1990 surveys, nymphal densities did not decline as distance from the vineyard edge increased. In 1991, however, nymphal densities were significantly higher at vineyard edges than in vineyard interiors in July, suggesting that oviposition initially was aggregated at vineyard edges. Subsequently, nymphal densities at vineyard edges and interiors were similar. Cumulative degree days (DD) for mean observation of first nymphs, first-generation, and second-generation peak populations, sampled at 14 vineyards in 1989, 1990, and 1991, were 390 ± 71, 648 ± 86, and 1,190 ± 154 DD (mean ± SD; base 10°C), respectively. Nymphal densities exceeded a provisional threshold of five per leaf in only 2, 25, 13, and 8% of vineyards untreated with insecticides in 1989, 1990, 1991, and 1992, respectively. These results show that leafhoppers do not cause economic injury in most New York vineyards in most years. Reduced insecticide strategies recently implemented for grape berry moth control will not greatly increase the need for insecticide applications directed at leafhoppers in New Yor

Fast Attitude Maneuvers for the Lunar Reconnaissance Orbiter

This paper describes a new operational capability for fast attitude maneuvering that is being developed for the Lunar Reconnaissance Orbiter (LRO). The LRO hosts seven scientific instruments. For some instruments, it is necessary to per-form large off-nadir slews to collect scientific data. The accessibility of off-nadir science targets has been limited by slew rates and/or occultation, thermal and power constraints along the standard slew path. The new fast maneuver (FastMan) algorithm employs a slew path that autonomously avoids constraint violations while simultaneously minimizing the slew time. The FastMan algo-rithm will open regions of observation that were not previously feasible and improve the overall science return for LRO's extended mission. The design of an example fast maneuver for LRO's Lunar Orbiter Laser Altimeter that reduc-es the slew time by nearly 40% is presented. Pre-flight, ground-test, end-to-end tests are also presented to demonstrate the readiness of FastMan. This pioneer-ing work is extensible and has potential to improve the science data collection return of other NASA spacecraft, especially those observatories in extended mission phases where new applications are proposed to expand their utility

Effects of Resistance to Bt Cotton on Diapause in the Pink Bollworm, Pectinophora gossypiella

Fitness costs associated with resistance to Bacillus thuringiensis (Bt) crops are expected to delay the evolution of resistance. In a previous study where pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae), larvae overwintered in outdoor insectaries, individuals from Bt-resistant strains had lower survival than individuals from Bt-susceptible strains or F1 progeny from crosses between resistant and susceptible adults. To investigate the physiological basis of such recessive cost, diapause duration was experimentally manipulated in the laboratory. Compared to a Bt-susceptible strain and F1 progeny, we hypothesized that Bt-resistant strains could exhibit a lower propensity or intensity of diapause, faster weight loss during overwintering, lower initial weight of diapausing larvae, and reduced longevity of moths emerging from diapause. Results were as expected for initial weight of diapausing larvae and longevity of overwintered male moths or female moths remaining in diapause for a short period. However, a higher diapause induction and intensity and slower weight loss occurred in F1 progeny and Bt-resistant strains than in a Bt-susceptible strain. Moreover, F1 progeny had greater overwintering survival than the Bt-resistant and Bt-susceptible strains, and F1 female moths had the greatest longevity after sustaining long diapausing periods. All of these unexpected results may be explained by pleiotropic effects of resistance to Bt cotton that increased the strength of diapause in the F1 progeny and Bt-resistant strains. Incomplete resistance was reflected in disadvantages suffered by Bt-resistant individuals feeding on a Bt diet instead of a non-Bt diet, including lower diapause propensity, lower diapause intensity and reduced longevity of overwintered male moths. While this study suggests that the evolution of resistance to Bt cotton and feeding on a Bt diet in Bt-resistant individuals have pervasive effects on several traits associated with diapause, further field experiments are needed to elucidate the basis of the overwintering cost in the pink bollworm

spatially-explicit test of the refuge strategy for delaying insecticide resistance

The refuge strategy is used worldwide to delay the evolution of pest resistance to insecticides that are either sprayed or produced by transgenic Bacillus thuringiensis (Bt) crops. This strategy is based on the idea that refuges of host plants where pests are not exposed to an insecticide promote survival of susceptible pests. Despite widespread adoption of this approach, large-scale tests of the refuge strategy have been problematic. Here we tested the refuge strategy with 8 y of data on refuges and resistance to the insecticide pyriproxyfen in 84 populations of the sweetpotato whitefly (Bemisia tabaci) from cotton fields in central Arizona. We found that spatial variation in resistance to pyriproxyfen within each year was not affected by refuges of melons or alfalfa near cotton fields. However, resistance was negatively associated with the area of cotton refuges and positively associated with the area of cotton treated with pyriproxyfen. A statistical model based on the first 4 y of data, incorporating the spatial distribution of cotton treated and not treated with pyriproxyfen, adequately predicted the spatial variation in resistance observed in the last 4 y of the study, confirming that cotton refuges delayed resistance and treated cotton fields accelerated resistance. By providing a systematic assessment of the effectiveness of refuges and the scale of their effects, the spatially explicit approach applied here could be useful for testing and improving the refuge strategy in other crop-pest systems. pesticide resistance | predictive evolutionary models | pest management | resistance management P opulation growth will continue to favor agricultural intensification for decades. Because agricultural intensification is associated with increased pest pressure, pesticides generally help to increase yield (1-3). Although significant progress has been made to reduce reliance on pesticides (4, 5), an increasing number of insects and mites exhibit field-evolved resistance to synthetic pesticides, Bacillus thuringiensis (Bt) sprays, and transgenic Bt crops (6, 7). Negative consequences of resistance include increased pesticide use, disruption of food webs and ecosystem services, increased risk to human health, and loss of profits for farmers and industry (1, 3). One of the main strategies for delaying resistance promotes survival of susceptible pests by providing refuges, which are areas of host plants where pests are not exposed to an insecticide. Theory predicts that refuges will slow the evolution of resistance by reducing the fitness advantage of resistant individuals (7-9). Refuges can also reduce the heritability of resistance when susceptible individuals mate with resistant individuals surviving exposure to an insecticide (7). Empirical support for the refuge strategy was provided by short-term laboratory and greenhouse experiments (10, 11). Although these experiments test the hypothesis that mating between susceptible and resistant individuals delays the evolution of resistance, they do not consider several factors that affect resistance in the field (7-9), and thus only provide partial support for effectiveness of the refuge strategy in the field. Retrospective analyses of variation in resistance evolution in the field also suggest that refuges have been effective, but these previous tests have been based primarily on comparisons among species, or qualitative comparisons within species based on a limited number of widely separated geographic areas (12, 13). In such tests, factors that vary among species or geographic areas can confound the effects of refuges. Accordingly, large-scale field tests of the refuge strategy for a single species within a geographic area where factors affecting resistance are similar are needed to test the refuge strategy more rigorously. Moreover, tests of predictive refuge strategy models are required to determine if the refuge strategy can delay resistance (14). Furthermore, to improve our ability to develop efficient refuge strategies, empirical approaches are necessary to characterize effects of refuges on resistance evolution (7, 15). Here we tested the refuge strategy using 8 y of data on refuges and resistance to the insecticide pyriproxyfen in 84 populations of the sweetpotato whitefly (Bemisia tabaci) sampled in cotton fields of central Arizona. We studied the B biotype of B. tabaci, also known as the Asia Minor-Middle East 1 species, which is a key pest of cotton and other crops in Arizona and worldwide (16). The insect growth regulators pyriproxyfen (a juvenile hormone analog) and buprofezin (a chitin synthesis inhibitor) are selective insecticides that have been used for whitefly control in Arizona cotton (Gossypium spp.) since 1996 (17, 18). A single application of either insecticide on cotton when B. tabaci populations start to increase has substantially reduced sprays of broad-spectrum insecticides, helped to conserve natural enemies, and restored farmers ' profits (18, 19). To deter rapid evolution of resistance, farmers in Arizona generally have not used pyriproxyfen to control B. tabaci on crops other than cotton Although B. tabaci is polyphagous, few whitefly crops other than cotton are available in central Arizona from June to September, when pyriproxyfen is sprayed on cotton. In principle, crops that could act as refuges include spring melons (Citrullus lanatus and Cucumis melo), alfalfa (Medicago sativa) and cotton not treated with pyriproxyfen (referred to hereafter as untreated cotton). B. tabac

Beet Armyworm Resistance to Cry1Ac

Susceptibility of beet armyworm, Spodoptera exigua Hübner, to the Bt toxin, Cry1Ac, expressed in the first generation of transgenic cotton plants was evaluated using a laboratory strain and several foreign and United States field strains. A diet-incorporation assay of neonate larvae was used. Susceptibility was estimated by the degree to which Cry1Ac inhibited larval growth from the first through fifth instar. Regression analyses of larval weights against log concentration of Cry1Ac yielded slope and intercept values that were used to compute I₅₀s, defined as the amount of Cry1Ac that resulted in a fifty percent reduction in larval growth. Three populations exhibiting reduced susceptibility to Cry1Ac were selected on diet containing 1000 micrograms of Cry1Ac per gram of diet. I₅₀s for non-selected populations ranged from 0.0477 micrograms Cry1Ac per gram of diet for the laboratory reference strain to 4.31 micrograms of Cry1Ac per gram of diet for a field strain collected from Yuma, Arizona. Selection of a strain from Belle Glade, Florida, with Cry1Ac yielded the lowest susceptibility to this toxin. Prior to selection, the I₅₀ was 2.43 micrograms of Cry1Ac per gram of diet; after selection the I₅₀ was 17.4 micrograms of Cry1Ac per gram of diet. Thus selection reduced susceptibility of the Belle Glade, Florida strain to Cry1Ac by 7.2-fold and yielded susceptibility that was 360-fold less than the laboratory reference strain. Selection also reduced susceptibility of an Arizona (Dome Valley) population by 3-fold. Our results demonstrate the presence of large (>25-fold) differences in susceptibility of field-collected beet armyworm populations to Cry1Ac. Furthermore, the fact that resistance was elevated three to seven-fold in two selected strains provided evidence of a genetic basis of resistance to Cry1Ac

Management of Pyrethoid-Resistant Whiteflies in Arizona Cotton: Selection, Cross-Resistance, and Dynamics

In 1995, silverleaf whitefly, Bemisia argentifolii Bellows and Perring, resistance to the widely -used mixture of Danitol® (fenpropathrin) + Orthene® (acephate) was shown to be severe and widespread in Central Arizona cotton. Thereafter, laboratory experiments were undertaken to identify the other major insecticides that were affected by this resistance. Whiteflies were collected in November of 1995 from Maricopa (highly resistant) and Yuma (relatively susceptible) County locations in Arizona. A composite colony was established by combining Yuma and Maricopa whiteflies in a 4:1 ratio. After six generations of adult selection of this population with Danitol + Orthene, appreciable shifts in the concentration responses for pyrethroid, organophosphate, and carbamate insecticides were observed, indicating heritable variation for resistance in the source populations. From this we obtained definitive proof that resistance to Danitol + Orthene confers cross-resistance to Asana® (esfenvalerate), Capture® (bifenthrin), Danitol, Decis® (deltamethrin), Decis + Orthene, and Karate® (lambda-cyhalothrin). Additionally, selection with Danitol + Orthene resulted in statistically significant reductions in susceptibility to Curacron® (profenofos), Lannate® (methomyl), Monitor® (methamidaphos), and Ovasyn® (amitraz). Studies were performed to assess tolerance of Maricopa (pyrethroid- resistant) and Yuma (pyrethroid-susceptible) populations to a diversity of conventional insecticides currently registered for use in Arizona cotton, with the intention of finding compounds that showed promise for overcoming pyrethroid resistance. Of the materials evaluated, Curacron, Lannate, Lorsban® (chlorpyrifos), Ovasyn, Supracide® (methidathion), and Vydate® (oxamyl) were most promising. To determine to what degree pyrethroid resistance in cotton influenced resistance in winter vegetables and melons, and vice versa, whitefly populations were collected from a succession of these crops in Western and Central Arizona regions. In most instances, the whiteflies in Western Arizona were significantly more susceptible to Danitol + Orthene than those in Central Arizona. Significant decreases were found in susceptibility to Danitol + Orthene during the 1996 season at three of the four locations in which multiple crops were monitored. This emphasizes that pyrethroid resistance levels can be increased in whitefly populations from any of the cotton, melons, or other winter vegetable crops evaluated. Therefore, management of pyrethroid resistance in Arizona cotton will require harmonizing resistance management efforts and specifically limiting pyrethroid use in the entire crop complex